There has been known a distillation apparatus that uses a distillation process. For example, Patent Literature 1 discloses a separation process module including a separator, a compressor, a heat exchanger, and a cooler. The separator separates input fluid including a first component and a second component different from the first component into first output fluid including the first component and second output fluid including the second component. The compressor compresses the first output fluid separated by the separator. The heat exchanger causes the first output fluid compressed by the compressor and the second output fluid separated by the separator to perform heat exchange. The cooler cools the first output fluid after performing the heat exchange in the heat exchanger. The first output fluid flowed out from the cooler and the second output fluid flowed out from the heat exchanger are respectively returned to the separator.
In this separation process module, thermal energy of the first output fluid flowed out from the separator is input to the heat exchanger, whereby the second output fluid flowed out from the separator is heated in the heat exchanger. That is, a reduction in thermal energy necessary for the heating of the second output fluid (energy saving) is achieved by efficient use of thermal energy of the first output fluid.
In the separation process module described in Patent Literature 1, the first output fluid flowed out from the separator is compressed by the compressor and then led into the heat exchanger, whereby the thermal energy of the first output fluid is collected. Therefore, when the first output fluid includes, as the first component, a component, direct compression of which is difficult, (e.g., a component that becomes extremely unstable during high pressure or a component that swells a seal section of the compressor), it is difficult to use the separation process module.
In a distillation plant described in Patent Literature 2, thermal energy of tower top vapor is input to a storage evaporator by using a heat pump. That is, in the distillation plant of Patent Literature 2, thermal energy of fluid flowed out from a top au column (a separator) is indirectly collected by using the heat pump without directly compressing the fluid in a compressor.
In a distillation apparatus described in Patent Literature 3, thermal energy of tower top, vapor is indirectly collected by a distillation reboiler by using a heat pump that uses water as a medium. Patent Literature 3 mentions that load adjustment of the heat pump is performed by adjustment of opening degrees of a compressor bypass and an inlet vane or by control of the number of revolutions of a compressor.
In the distillation apparatus described in Patent Literature 3, although the adjustment of the load of the heat pump is performed, there is a limit in an amount of the adjustment. In other words, in the distillation apparatus described in Patent Literature 3, it is difficult to flexibly cope with fluctuation in a flow rate of fluid flowed out from a top of a separator.